When icy, water-rich oceanic planets migrate towards their star, the ice melts and eventually forms a thick atmosphere of water vapour, increasing their radius.
Exoplanets with a radius twice that of the Earth are rare. A team from MPIA, UNIGE and UNIBE has come up with new explanations. When icy, water-rich oceanic planets migrate towards their star, the ice melts and eventually forms a thick atmosphere of water vapour, increasing their radius. Thomas Müller / MPIA Why are so few exoplanets about twice the size of Earth detected? On the basis of computer simulations, a team from the Max Planck Institute for Astronomy (MPIA) and the Universities of Geneva (UNIGE) and Bern (UNIBE) has confirmed that the migration of sub-Neptunes planets - water-worlds - could explain this absence. As these planets move closer to their central star, the water ice that evaporates forms an atmosphere that makes them appear larger than in their frozen state, well beyond twice Earth's radius. At the same time, smaller rocky planets, are gradually losing part of their original gaseous envelope, leading to a significant reduction in their radius. These results open up new perspectives for the study of exoplanets.
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